Traffic volume studies are conducted whenever it is desired to know the number of vehicles or pedestrians passing a point, entering an intersection, or utilizing a particular facility such as a traffic lane, crosswalk, or sidewalk. Such counts are merely a sample of actual volumes and the sampling period may range from a few minutes to a week or more at a given location.
The reasons for making volume counts may vary significantly. Counts are utilized to determine the composition and amount of traffic on roadways; to determine the number of vehicles traveling on, in, or through an area; to evaluate accident data; to serve as a basis for traffic signal timing; to obtain data useful for planning for new roadways and determining geometric designs; to determine growth trends; and many other purposes.
The kind of information collected and tabulated also varies. In some cases, details on the composition of vehicles in a traffic stream are required, while others require specific data on pedestrian and vehicle directional movements.
The two basic methods of obtaining traffic counts at the present time are mechanical devices which automatically record certain traffic events, and manual counts taken by field personnel.
Most mechanical devices for making automatic counts are used when only a simple tabulation is needed of number of vehicles; i.e., no separation of vehicle type, direction, turning movements, pedestrians, lane use, etc. There are three general types of portable mechanical counters currently known to be in use: (1) junior counter, which is a continuation-type totalizer counter with a visual numerical register and is powered by a dry cell battery; (2) period counter, which is a special version of the junior counter and which has a time clock that can be set to activate the counter at a specific time and then run only for a definite length of time; and (3) senior counter, which is a recording-type counter that contains a clock, a reset-type stamping and/or punching mechanism or event pens, a roll of tape or a circular chart, and that is powered by batteries. Each of these counters utilizes devices to sense vehicle movement over a given point in the roadway and then increment the counting register. There are several types of detection or sensing devices currently in use including the road tube, electric contact plates, photocells, radar magnetic or magnetometer detectors, ultrasonic and infra-red detectors, and induction loops.
Junior counters do not provide a printed record of volume counts, so the count accumulator must be read and recorded at the field location at the beginning and completion of each counting period.
The senior counter recorder stores vehicle actuations in an accumulating register, and, upon clock actuation, prints the results at pre-selected intervals. Several methods are available for recording the count data, such as printed tape, circular charts and punch tape.
In general, the compilation of traffic counts from mechanical devices into useable summary formats requires a considerable amount of manual tabulation. Data reduction is therefore expensive and time-consuming. However, punched tape can be processed through a translator which, when connected to a keypunch or reader, will produce count tabulations more efficiently than other current methods.
The aforesaid manual counting is a method of obtaining volume data through the use of field personnel known as traffic checkers. Manual counting is required when the information desired cannot be obtained through mechanical devices. This includes the classification of vehicles by size, type, number of occupants or other features, the recording of turning movements at intersections, and other specific vehicular or pedestrian movements. Basically, manual counting methods have not advanced much in recent times, and consist essentially of observers utilizing tally marks to record observations.
Today, the basic device employed almost universally to conduct manual traffic counts is the tally counter which is simply a mechanized tally marker that eliminates the need for checkers to take their eyes off the roadway to make tally marks. These counters are usually mounted in banks (one bank for each intersection approach) on a clipboard.
Counter totals are transferred by the checkers at specific time intervals to field sheets tailored for each counting location. Field sheets are set up for whatever time period is desired, i.e., five, fifteen, thirty, or sixty minute periods. A new tally sheet must be utilized for each discrete time period observed. These sheets must then be tabulated by office personnel and manually transferred to a volume count summary form by time period, approach, and directional movement.
While the manual counting method or device has remained somewhat primitive, some improvements have taken place with regard to transcribing the tally register totals and the preparation of tabulated summaries.
Mark-sense data processing cards have been used for some years in lieu of the time interval tally sheets. These cards greatly reduced the data reduction effort required by office personnel. However, due to continual mechanical problems encountered with card reading devices processing mutilated cards returned by field personnel an alternative method of recording data was devised, and in recent years an optical scanning form for tally sheets has been used in lieu of mark-sense cards.The marked optical scanning sheets are processed through a reader which transcribes the data onto magnetic tape. The magnetic tape is then delivered to a suitable computer for processing. A tabulated event summary by time period is returned from the computer in the form of a hard copy printout for traffic analysis.
The portable electronic traffic event recording apparatus of the present invention eliminates all of the aforesaid tally cards or sheets and requires for each traffic count only that the traffic checker be posted at a vehicle passageway or intersection with a corresponding suitable traffic pattern display board mounted on the recording apparatus, and the apparatus with display board suitably oriented to the passageway or intersection. After the checker has put a signature switch on the apparatus to the ON position, he need only observe the traffic events as they occur, depressing at each occurrence one of a number of push button switches respectively corresponding to the location and character of each event desired to be observed and recorded as displayed on the display board. Each switch depression creates an electrical signal which is recorded in an electronic memory contained in the recording apparatus, and each such signal is automatically recorded in the memory with an identity as to its particular switch source and the particular time period within which it occurred. The usual five minute time periods preclude the possibility of data fabrication, provide a record of on-off times and checker diligence, and eliminate the need for the checker to transfer count data to tally sheets or to keep track of time intervals.
When a period of counting is complete, the portable recording apparatus of the present invention may be plugged in to a master computer which will automatically extract the recorded data from the portable apparatus, process the data for one or more counts according to the master computer's predetermined software program, and print out a tabulation of each count in an appropriate form as determined by the program of the master computer.
The present invention eliminates time waste, possibility of confusion and fabrication of data, paper shuffling by field or office personnel, and reduces traffic counting to its simplest elements.